The present invention relates to an improved method and product of folding a sheet, such as paper or cardboard, such that by its inherent fold memory, it is capable of automatically collapsing itself to, or unfolding itself from, a compact folded condition. These folded products are conveniently used, for example, as maps or reference guides that when folded can fit in one's pocket or purse.
Known folding configurations for such products typically form outer rectangular panels with V-shaped ends tapering toward the center of the sheet, which may be affixed to a backer or stiffened cover, and side pleats which dovetail between the outer panels in the folded condition. A good example is shown in U.S. Pat. No. 3,753,558 to Sheroff et al. having an inner pleat and a pair of opposing end pleats that fold between the outer panels.
However, such known configurations have the problem that the end pleats must be comparatively short in length and width in order to avoid binding with its opposite pleat when returning to its folded condition. Because of this limitation, the underlying sheet is restricted in dimensions to rectangles of length not substantially greater than width, and/or to widths which are not substantially greater than twice the width of the product in its folded condition. These restrictions limit the attractiveness of the product and the size of the sheet that can be used for a product that will fit in a pocket or purse in its folded condition. Moreover, the end pleats have a tendency to bind even with sheets of the restricted dimensions.